Except it does not mean what it sounds like and how the media interprets it:
1,000-year rainfall event definition:
A 1,000-year rainfall event is measured by the amount of rain over a particular period of time. We use a technique to define this called a Point Precipitation Frequency Estimate curve. This is what it looks like for Columbia, SC. Below and you can see almost no matter the amounts or time scale this was a 1,000-year rainfall event. It does not mean it hasn’t rained this much in 1,000 years, or this is the most rain in 1,000 years. It’s a recurrence statistic.
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In both cases neither means this only happens every 1,000-years or it hasn’t happened in 1,000 years. This is a statistical measuring stick meaning each has a 1 in 1,000 chance of happening in any given year. Or if you like percentages there is a 0.1% chance of a 1,000-year flood or rain event every single year for any location. Same goes for 100-year events, there is a 1% chance of a 100-year flood or rain event every year.
1,000 Year rainfall event vs 1,000 year flood, what that actually means. – @wxbrad Blog
